General Bishop

How does Heal and Holy Symbol work? I recently made a cleric last week and soon will become a priest in no time; however, I realized when I was training in my 3x, that heal doesn't necessarily heal 100% of my hp at lvl 10, so I wanted to know if there was a way to accurately measure how much hp you can restore with heal. Since I'm almost going to become a priest, I wanted to how Holy Symbol works since I believe all it says is 150% exp at max level and it says with at least 2 ppl. I don't think it means if I have 6 ppl, each person will get 150% exp each, or maybe it does, I don't know. Can someone please explain these two skills to me? Thank you :D